In an automobile, the windshield, which comprises laminated glass, is connected to the car body by a molding. A molding-less automobile, which has a molding invisible from outside in consideration of car design, has been known. Since the peripheral portion of the windshield is exposed outside in this case, a fired substance, such as e.g. black ceramic, is formed on a peripheral portion of the inner side (inner surface) of the outer sheet as the outer glass sheet of laminated glass bent in a convex shape, for the purpose of concealment and protection for an intermediate film. Since pins for fitting the windshield into the car body are bonded to a peripheral portion of the inner side (inner surface) of the inner sheet, a fired substance is also formed on this portion for the purpose of preventing an adhesive from being degraded by, e.g., ultraviolet light or another purpose. Such laminated glass is configured so that the fired substance (black ceramic) on the inner surface of the outer sheet is sandwiched between the outer sheet and the inner sheet. In Description, in laminated glass comprising two glass sheets bonded together through an intermediate film, the glass sheet that is positioned on the convex side of the laminated glass bent in a convex shape (the side of the laminated glass with the glass surface formed in a convex shape) is called the outer sheet, and the glass sheet that is positioned on the concave side of the laminated glass (the side of the laminated glass with the glass surface formed in a concave shape) is called the inner sheet.
When such laminated glass is produced according to a conventional technique, glass sheets are cut to have predetermined shapes to form an inner sheet and an outer sheet and a treatment of edges (chamfering) are conducted to these inner and outer sheets. Then, to the inner sheet, paint for fired substance is printed (screen-printed) on a peripheral portion of the inner surface and the inner sheet is dried at about 100° C. to evaporate the solvent. To the outer sheet, the paint for fired substance is also printed on a peripheral portion of the inner surface, followed by drying, and then, the outer sheet is heated to the firing temperature of ceramic in a forming furnace for firing to carry out a firing step to the paint for fired substance. Then, the inner sheet and the outer sheet are overlapped each other through a mold-releasing agent before they are conveyed into a bend-forming furnace and in this forming furnace, a bend-forming step is carried out to the inner and outer sheets along with the firing of the paint for firing substance on the inner sheet. The reason that the firing to the paint for fired substance on the outer sheet conducted separately from the step to the inner sheet, is as follows. If the firing is carried out in a state that the inner and outer sheets overlap each other, there may result disadvantages such as the separation of the fired substance sandwiched between the inner and outer sheets, the transfer of the fired substance onto the inner sheet, the bonding of the inner and outer sheets and so on, such being undesirable for the quality.
Then, the inner sheet and the outer sheet, which have been bend-formed in an overlapping state, are separated and washed to remove the mold-releasing agent. The inner and outer sheets are again overlapped through an intermediate film such as PVB (polyvinyl butyral) and they are press-bonded under vacuum. Thus, laminated glass is completed.
However, in the above-mentioned production method for laminated glass, it is necessary to carry out the firing step for the fired substance on the outer sheet separately from the bend-forming step to the inner sheet and the outer sheet. Accordingly, it takes extra work and is troublesome. Further, a slight deformation may result in the outer sheet in the firing step for the fired substance on the outer sheet. This is troublesome in that for example, the outer sheet does not overlap on the inner sheet in the bend-forming step conducted subsequently.
On the other hand, laminated glass having a fired substance between an inner sheet and outer sheet is described in Patent Document 1.
The purpose of the production method for laminated glass described in Patent Document 1 is to bend a glass sheet along with firing to a covering layer formed on either recessed surface (inner surface) or a protruded surface (outer surface) or both surfaces of the glass. For that purpose, the covering layer is fired while the glass sheet is floated and transferred in a heating furnace by means of a transferring device which jets out hot air to the lower surface of a glass sheet having a covering layer to be fired and at the same time the glass sheet is bent by heat at a glass sheet softening temperature.
Namely, according to this bending method, glass sheets are conveyed with buoyancy one by one so that the glass sheets with covering layers made of e.g. paint of black ceramic on any of the projected surface and the recessed surface can be conveyed into the forming furnace in which the glass sheets are bent one by one with an upper mold and a lower mold for pressing.
In the production method for laminated glass described in Patent Document 1, however, a large-sized device with completed structure is needed because it employs a float conveyor jetting out hot air. In addition, since glass sheets are bent one by one, a slight displacement may result in the formed product even with the same bending mold, or there is a change of forming conditions such as forming temperature or error of dimension in the shape of glass sheets. Accordingly, it is difficult to coincide completely the radius of curvature or the shape with a curve, hence a slight fluctuation is unavoidable. When laminated glass is produced by overlapping such glass sheets which have been bent-formed separately, complete contact may not be obtained between the inner sheet and the outer sheet in the laminated glass. Further, such laminated glass invites cost increase and therefore, is not practical.
Patent Document 1: JP-A-6-340441